JPS6126596B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to aqueous ink compositions. In detail, it relates to water-based ink compositions suitable for writing instruments, stamps, printing, recorders, etc., and has water resistance,
It has excellent performance such as non-evaporation, heat and cold resistance, and storage stability over time, and can record clearly without bleeding or bleed through the paper, and when applied to writing instruments,
In addition to having the above-mentioned properties, it also provides suitable low viscosity and appropriate drying resistance, and even if the writing instrument is exposed to the atmosphere for a long time, the ink will always flow smoothly without clogging the ink flow path. , relates to an aqueous ink composition that enables smooth writing. Although various attempts have been made to provide water-based inks with the above-mentioned performance, satisfactory performance has not yet been achieved. For example, it is widely practiced to add glycol ether solvents or glycol solvents as evaporation inhibitors to the water-soluble dyes, but glycol solvents have high viscosity and low vapor pressure, so the ink evaporates. If a sufficient amount is added to suppress the ink, the viscosity of the ink will increase, and when used in the above-mentioned writing instruments that require low viscosity, the ink will not flow smoothly, the handwriting will be difficult to dry, and the handwriting will be resistant to staining. Due to disadvantages such as poor performance, the amount used is limited, and it is not possible to add enough to fully satisfy the performance.
Furthermore, since glycol ether solvents generally have a low surface tension, the handwriting of inks made using these solvents tends to smear and cause strike-through, which also limits their use. Furthermore, since the dissolving power of the dye is not sufficient, there are drawbacks such as the inability to obtain high-density color development. In terms of water resistance, in this type of ink, these solvents themselves lack the ability to impart water resistance, and even if new additives are added, there are restrictions as mentioned above, so it is difficult to achieve the desired result. performance cannot be obtained. On the other hand, in an attempt to improve these shortcomings,
JP-A-50-71423 discloses an aqueous ink composition using lactams such as 2-pyrrolidone and N-methyl-2-pyrrolidone. The addition of such lactams is effective in imparting dye solubility and water resistance, but on the other hand, it has the disadvantage that 2-pyrrolidone has a high melting point and easily freezes at temperatures below 20°C. If sufficient amounts of glycols are used in combination with these, the above-mentioned problem of increased viscosity will occur. In addition, N-methyl-2-pyrrolidone has a high dissolving power and swells or dissolves various plastic materials, such as vinyl chloride resin, polyamide resin, polystyrene resin, polyacrylic resin, etc., so its addition There are restrictions on the amount and applicable materials. The ink for writing instruments, which is mainly composed of direct dye and water and to which urea and polyhydric alcohol are added, as disclosed in Japanese Patent Publication No. 48-43301, exhibits effects such as dye solubility and moisture evaporation control, but is essential. Polyhydric alcohols such as ethylene glycol, propylene glycol, thiodiethylene glycol, and glycerin, which are used together as components, have a higher viscosity than the pyrrolidone derivatives used in the present invention, and therefore the resulting ink becomes highly viscous. It may clog the ink flow path in the writing instrument, making it impossible to maintain stable ink flow. In addition, performance such as water resistance and heat resistance stability is also insufficient. The present invention improves the defects found in conventional ink compositions as described above, further improves performance that cannot be achieved by these individual methods, and further improves the characteristic performance obtained by these individual methods. As a result of various researches aimed at providing a water-based ink composition that combines the various properties described at the beginning, we have found that urea, dye, and N-vinyl are essential components.
It has been found that this can be achieved by a specific composition containing 2-pyrrolidone and/or 2-pyrrolidone and water. To further describe the above in detail, in the ink composition, 5 to 40% by weight of urea, 1 to 15% by weight of dye, 2 to 30% by weight of N-vinyl-2-pyrrolidone and/or 2-pyrrolidone and In the above, N-vinyl-
The mixture contains a mixture of 2-pyrrolidone and 2-pyrrolidone in a weight ratio of 1:0.5 to 1:10, and a mixture of N-vinyl-2-pyrrolidone and 2-pyrrolidone and urea in a ratio of 1:0.5 to 1:10 by weight. Weight ratio: 1:0.5~
It has been found that a range of 1:2 is an effective combination. Add an explanation regarding the above. The amount of urea added is
In systems containing less than 5% by weight, almost no effect is observed. As the amount of urea added increases, the present invention works more effectively, but if it exceeds 40% by weight, urea tends to precipitate and the viscosity of the ink increases, making it difficult to use marking pens with capillary pen bodies or water-based pens. It is not preferable for writing instruments such as ink ballpoint pens in terms of ink followability. From this point of view, it is particularly effective to add urea in an amount of 15 to 30% by weight. When the amount of 2-pyrrolidone and N-vinyl-pyrrolidone added is less than 2% by weight, the effect is weak. If it exceeds 30% by weight, ink bleeding and handwriting bleed through may occur, which is undesirable. Dyes that can be applied include water-soluble acid dyes,
Direct dyes, etc. For example, eosin
GH (CI45380), Erythrosin (CI45430), Acid Violet 5B (CI42640), Patent Blue-AF (CI42080), Brilliant Cyanine 6B
(CI42660), Assisted Blue Black 10B (C.
I.20470) and other acidic dyes. In addition, deep plug XA (CI direct black)
154), Black G (CI35255), Water Black #100 (CI35255), Violet BB (C.
I.27905), Congo Red (CI22120), Direct Sky Blue 5B (CI24400), and Phthalocyanine Blue (CI74180). By configuring the present invention as described above,
Defects found in systems that use pyrrolidone derivatives, urea and polyhydric alcohols alone, and systems that use only these alone cannot achieve the desired performance, or even if they do, only certain limited performances can be achieved. In terms of performance, on the other hand, it can cause defects in performance,
These pyrrolidone derivatives or urea may be obtained for the first time at these sacrifices, or they may be used in a limited amount in order to prevent the occurrence of other defects, and the performance of these pyrrolidone derivatives or urea may not be effectively demonstrated and the product may be left unfinished. Only half-hearted performance is obtained. We have succeeded in obtaining a water-based ink composition that solves the conventional defects, further enhances the characteristic performance of each system without causing other defects, and combines various performances. be. This point will be specifically explained. It was discovered that the coexistence of urea and a pyrrolidone derivative when dissolved in water causes a significant freezing point depression.
The tendency of the ink to freeze has been eliminated, and in this system, it has been achieved that it does not freeze even at -10℃, and the low viscosity, evaporation control, dye solubility, and water resistance of pyrrolidone derivatives have been achieved. It was possible to fully demonstrate the remarkable performance in application etc.
At the same time, urea has the effect of improving dye solubility,
The effect of suppressing the evaporation of liquid components in the ink and the effect of suppressing the precipitation of dyes and other solid components can be exerted without using polyhydric alcohol as an essential component as seen in conventional methods. It is also effective against viscosity. The aqueous ink composition of the present invention obtained in this manner using a combination of urea and a pyrrolidone derivative is far superior to the comparative ink, as exemplified in the attached Table (1) Performance Comparison Table. In addition, it has properties such as water resistance, dryness resistance, cold resistance and freezing resistance, and has excellent heat resistance stability, and has effective performance such as no bleeding or bleed-through of handwriting on paper. In addition, by using urea and a pyrrolidone derivative in combination, it is possible to dissolve dyes such as direct dyes and acid dyes at high concentrations, and an appropriate dye can be selected to provide an aqueous ink composition with excellent light resistance. be able to. When applied to felt-tip pens, water-based ink ballpoint pens, etc., this kind of writing instrument can have a suitable low viscosity, and even if the writing part is exposed to the atmosphere for a long time, there will be no sudden increase in viscosity or breakage of solid content. To provide an aqueous ink composition which enables smooth writing without any blemish and by which ink always flows smoothly. Examples of the present invention will be described below regarding ink for writing instruments. In addition, parts in the following formulation examples indicate parts by weight.

【table】

【table】

[Table] For the example ink and comparative example ink, the ingredients in the formulation example, such as urea, pyrrolidone derivative, soda carbonate, and ethylene glycol, were first mixed in water, the dye was added with stirring, and the mixture was stirred at room temperature for about 2 hours. obtained by doing.

【table】

[Table] Although the examples of the present invention are described with respect to inks for writing instruments, they can also be applied to ink compositions for stamps, printing, recorders, etc. In that case, triethanolamine may be added as necessary. , amine solvents such as diethanolamine and monoethanolamine, various dyeing aids, ethylene carbonate, propylene carbonate, formamide,
Organic solvents such as dimethyl sulfoxide can be added. In addition, by adding appropriate viscosity,
It is effective to incorporate water-soluble resins to increase water resistance and prevent bleeding and bleed-through.
These include, for example, casein, silicone resin, maleic acid resin, styrene-maleic acid copolymer,
Examples include acrylic resins, cellulose derivatives, polyvinylpyrrolidone, and polyvinyl alcohol. In addition to these, it goes without saying that additives such as various surfactants and preservatives may be added as necessary.

Claims (1)

[Claims] 1 Urea, dye, N-vinyl-2 as essential components
- An aqueous ink composition containing pyrrolidone and/or 2-pyrrolidone and water. 2. The aqueous ink composition according to claim 1, comprising a mixture of 2N-vinyl-2-pyrrolidone and 2-pyrrolidone in a weight ratio of 1:0.5 to 1:10. 3. The water-based ink composition according to claim 2, wherein the ratio of the mixture of N-vinyl-2-pyrrolidone and 2-pyrrolidone to urea is 1:0.5 to 1:2 by weight.